That way is simpler.

It's also somewhat better for users who pass a filtered collection, **but:**
- We may undo this change in the future (as we are considering approaches that would actually use the result of `size` for more than an emptiness check).
- A nonempty filtered collection will still apply the filter at least once during the `isEmpty` call, so that can still cause trouble if the filter has side effects or "call the filter until it returns `true`" is slow enough to matter.
- Other methods in Guava likely still trigger similar behavior when given a filtered collection, as do methods outside of Guava.

Fixes #7143 (for now)

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PiperOrigin-RevId: 623232817